Ceramic components having multilayered architectures and processes for manufacturing the same

ABSTRACT

The present invention relates to multilayered ceramic components ( 10 ) and methods of fabricating such multilayered architectures. More particularly, the present invention relates to multilayered components having a plurality of dielectric ( 12 ) and electrode material ( 14, 15 ) layers. The multilayered components are manufactured by coextrusion processes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based on, and claims the benefit of, co-pending U.S.Provisional Application Ser. No. 60/293,596, filed on May 25, 2001,entitled “Coextrusion Melt Spinning Process for Fabricating ComponentsHaving Multilayered Architectures,” and incorporated herein byreference.

The present invention was made with U.S. Government support under grantNumber DASG60-01-P-0052 awarded by the U.S. Army Space and MissileDefense and under Award Number 9660898 from the National ScienceFoundation. Accordingly, the U.S. Government may have certain rights inthe invention described herein.

FIELD OF THE INVENTION

The present invention relates to multilayer ceramic components,including capacitors, and methods of manufacturing such components, moreparticularly, coextrusion processes for manufacturing composite ceramiccomponents having multi-layered architectures.

BACKGROUND OF THE INVENTION

The most common method for manufacturing multi-layer ceramic capacitors(MLCCs) involves tape-casting technologies. Unfortunately, tape-castingprocesses pose severe handling problems as the thickness of the tapedecreases. Although there has been a strong desire for a more versatileprocess than tape casting for fabricating MLCCs, other possiblefabrication methods, such has vapor deposition techniques and sol-geltechniques, have shortcomings that have impeded their commercialsuccess. For instance, chemical and physical vapor deposition techniquesare limited by their inherently slow deposition rates. In addition,sol-gel techniques are limited because sol-gel based components mustundergo large shrinkages during drying and firing.

In electronic circuitry, the demand for greater board densities andimproved volumetric efficiency in components is continuously escalating.In the case of MLCCs, smaller component parts and thinner dielectriclayers are required for improving the performance of electronic devices.This trend has driven the thickness of MLCC chips down from 0.120 inchesin the 1980s to 0.080 inches in the late 1990s. Presently, the industryis heading towards 0.060, 0.040, and even 0.020-inch thick MLCCs. Thesenumbers translate into dielectric layer thicknesses of approximately 20μm in the 1980s, layer thicknesses of 13-15 μm in the mid-1990s, andless than 7.5 μm layer thicknesses in the late 1990s. The technologypush worldwide has now seen the fabrication of dielectric layers of lessthan 5 μm and thicknesses will continue to decrease. In turn trends inmanufacturing will require new methods of MLCC fabrication with moreautomated production for large quantities of components.

Therefore, there remains a need for a versatile method for preparingthese thin film ceramic components for the electronics industry.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide methods ofmanufacturing electronic components having multi-layered structures,including components having layer thicknesses of 4 μm or less.

It is another object of the present invention to provide multi-layeredcomponents that include one or more dielectric material layers and oneor more electrode material layers, the layers having controlled anduniform thicknesses.

It is yet another object of the present invention to providecost-effective and efficient extrusion processes for forming multilayercomponents.

According to the present invention provides, a multilayer ceramiccomponent includes alternately stacked dielectric layers and internalelectrode layers. Methods of fabricating such components havingmultilayered architectures include combining a dielectric ceramicmaterial with a first additive composition to form a first compositeblend, combining an electrically conductive material with a secondadditive composition to form a second composite blend, forming adielectric body, such as a sheet, from the first composite blend,forming an electrode body, such as a sheet, from the second compositeblend, arranging a plurality of dielectric bodies and electrode bodiesto form a feed rod having a patterned array of alternating dielectricand electrode layers, and extruding the feed rod to form a “green”component product having multi-layered architecture. The “green”component product then is cut into individual component pieces which arethen finished. Finishing steps include a binder bake out step and adensification step to provide a fully consolidated and densifiedfinished component product.

The finished components have improved durability and strength ascompared to monolithic ceramic components. By varying the materialsselected for the dielectric and electrode layers, desired mechanicalstrengths and electrical properties can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an elevational cross-sectional view of a multilayer ceramicchip capacitor in accordance with the present invention;

FIG. 2 is a schematic block flow diagram showing a method ofmanufacturing a multilayer ceramic component, such as the capacitor ofFIG. 1, in accordance with the present invention;

FIG. 3 is a schematic flow diagram showing steps of the method of FIG.2; and

FIG. 4 is a top plan view of the green product FIG. 2 showing possiblecut locations for forming a plurality of ceramic components from thegreen product.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates to microfabrication by coextrusionprocesses for manufacturing multilayered ceramic components. Inaccordance with the present invention, it is possible to fabricatemultilayered components in a wide range of sizes, including multilayeredarchitectures with layer thicknesses of 4 μm or smaller, with uniformlayers. The components have improved durability and strength as comparedto monolithic ceramic components. The components also exhibit desiredmechanical strengths and electrical properties, which can be modified byvarying the materials used for the dielectric and electrode layers. Inone embodiment, the materials used in the ceramic component areco-firable. Although the present invention provides for the fabricationof a variety of components, including multi-layered ceramic capacitors,microwave dielectric filters, multilayer piezoelectric actuators,ultrasonic motors, connectors, timing devices and energy storagedevices, the invention will be described herein with reference tomultilayer chip capacitors that include a plurality of dielectricceramic and electrode layers.

As used herein, “dielectric ceramic” is intended to mean generally anonconducting ceramic material. Such materials may be used as capacitiveelements in electrical circuits and as electrical insulation. Electricalproperties that may be optimized when designing such circuits typicallyinclude the dielectric constant, dielectric loss factor, and dielectricstrength of the material. In general, dielectric ceramics are classifiedbased on their permittivity. Class I dielectrics include lowpermittivity ceramics with dissipation factors of less than about 0.003,and medium permittivity ceramics with dissipation factors between about15 to about 500. Dielectrics having a permittivity less than 15 arecommonly referred to as insulators. Class II dielectrics include highpermittivity ceramics with dissipation factors between about 2000 toabout 20,000.

In an embodiment of the present invention, the critical factor is theperformance of the resulting component such as a capacitor. Accordingly,the performance required for the capacitor is determined. Theperformance required determines what dielectric is used. Once adielectric has been selected, an electrode is selected as a complimentto the dielectric.

Referring to FIG. 1, there is illustrated an exemplary structure of amultilayer ceramic chip capacitor 10 (MLCC). The capacitor 10 has aplurality of alternately stacked layers of dielectric layers 12 andinternal electrode layers 14, 15. External electrodes 16, 17 aredisposed at side surfaces 18, 20 of the capacitor 10. The externalelectrodes 16 are in electrical connection with the internal electrodelayers 14, 15. The internal electrode layers 14, 15 are arranged in anoffset configuration so that adjacent electrodes 14, 15 extend fully toand are exposed at opposite side surfaces 18, 20. That is, one group ofelectrodes 14 is exposed at a first side surface 18 and is in contactwith one of the external electrodes 16, and a second group of electrodes15 is exposed at a second side surface 20 and is in contact with anexternal electrode 17 different from the first external electrode 16.

Although a rectangular shaped capacitor is generally described herein,components having various geometries are contemplated as being withinthe scope of the present invention. Additionally, the size of thecomponent is not critical, and the component may be dimensionedaccording to the particular application in which it will be used.Typical dimensions range between about 0.012 inches to about 0.60 inchesin length and between about 0.06 inches to about 0.54 inches in width.

Referring now to FIGS. 2 and 3, the process of producing microlayeredstructures by co-extrusion in accordance with the an embodiment of thepresent invention includes: separately blending (as at 24) the startingmaterials 21 for dielectric layers, and separately blending (as at 26)the starting materials 22 for electrode layers; forming a dielectricmaterial sheet 50 and an electrode material sheet 52 (as at 28 and 30respectively); cutting and stacking the sheets 50, 52 (as at 31 and 32respectively); forming a feed rod (as at 34) from the stacked sheets 50,52; consolidating (as at 37) and extruding (as at 38) the feed rod 36one or more times to provide a ceramic green product (as at 40);finishing the green product (as at 42); and forming end terminations (asat 44) at outer surfaces of the finished component to provide a finishedproduct in accordance with the present invention.

Referring to FIG. 2, raw powders of dielectric material 23 and electrodematerial 25 are separately blended (as at 24, 26) with desired additives27, 29 to provide composite blends. Raw powders of ferroelectriccompounds may be used as the dielectric material 23. Titanate compounds,niobate compounds, tantalate compounds, any other suitablenon-conductive material, and combinations thereof also may be used.Examples of suitable compounds include MgTiO₃, BaTiO₃, BaTi₄O₉, TiO₂,SrTiO₃, CaTiO₃, Al₂O₃, and MgO, and the like. Metallic powders,including base metal powders such as nickel, copper and iron, preciousmetal powders, other suitable conductive materials and combinationsthereof may be used as the electrode material 25. Design requirements,such as interlayer thicknesses, which is identified based on applicationand performance requirements, should be considered when selecting theparticle size of the raw powders. Generally, raw powders having particlesize distributions in the range of about 0.01 to about 100 microns (μm)in size may be used. Preferably, the particle size of the powder isbetween about 1 to about 10 microns. The particle size of the powdersselected limits the thickness of the layers of the components. That is,the layers can be only as thin as the maximum diameters of the powdersused.

The raw powders may be milled in a solvent using dispersants to controlthe surface chemistry of the powders prior to blending 24, 26 to enhanceblendability. Milling stations such as commercially available fromBoston Gear, Boston, Mass. may be used as needed to ball mill the powderto obtain the desired size distribution. The ceramic/solvent blend isball milled with milling media such as silicon nitride (Si₃N₄) orzirconium oxide (ZrO₂) thus creating a ball-mill slurry. Sintering aidssuch as, for example, aluminum oxide (Al₂O₃) and yttrium oxide (Y₂O₃)additions to Si₃N₄, when necessary, are added and milled together withthe ball mill slurry. The powders are milled for a time effective forproviding desired particle sizes and distribution. Typical milling timesare between about 24 to about 120 hours, depending on the startingpowder material.

The milled or, if milling is not needed, the as-received powders aremechanically blended 24, 26 to obtain desired dispersioncharacteristics. The blending 24, 26 may be in a high shear mixer, suchas those commercially available from C.W. Brabender of South Hackensack,N.J. or from Thermo Haake of Paramus, N.J. If the powders are notmilled, sintering aids, when necessary, are blended together with theraw powders during blending. Smooth, uniformly suspended dielectric andelectrode composite blends are formed by the blending step 24, 26.

Additives 27, 29 may be blended with the powders during blending, asdesired, to enhance the material characteristics and processability ofthe powder blends. Additives 27, 29 may include thermoplasticmelt-spinnable polymer binders, plasticizers, waxes, and othermodifiers. Examples of thermoplastic binders include ethyleneethylacetate (EEA) commercially available as DPDA-618NT from UnionCarbide, ethylene vinylacetate (EVA) commercially available as ELVAX 470from E.I. DuPont Co., and Acryloid Copolymer Resin (B-67) commerciallyavailable from Rohm and Haas, Philadelphia, Pa. Examples of plasticizersinclude heavy mineral oil (HMO) commercially available as Mineral OilWhite, Heavy, Labguard® and methoxy polyethyleneglycol having amolecular weight of about 550 (MPEG-550) commercially available fromUnion Carbide. Addition of thermoplastic binders allows forming of thematerials under heating conditions. The composite blends are compoundedat about 150° C. while metering a viscosity-modifying additive until aviscosity is obtained that will ensure desired proper rheology for anextrusion process. The viscosities of the composite blends should besuch that the blends can be pressed into sheets, can be cut throughwhile in sheet form, can withstand repeated heating and coolingconditions, and can be co-extrudable through an orifice of predeterminedgeometry. Preferably, the viscosities of the dielectric and electrodecomposite blends are similar to one another to provide generallyconsistent co-extrusion of the blends.

Because the mixers have fixed volume reservoirs, the recipes for thethermoplastic/ceramic blends produced in batches are formulated on avolumetric, as opposed to a gravimetric basis. As an example, one blendconsists of between about 45 to about 75 vol. % of the ceramic powder,between about 15 to about 50 vol. % of the thermoplastics, and betweenabout 0 to about 10 vol. % of the plasticizers. Thus, the mass of abatch of ceramic/thermoplastic varies with the density of the ceramicpowder.

Composite blends can be readily obtained with optimum plasticity andsolid loadings in the range of 50 to 60 vol. %, or even higher loadingsutilizing a bimodal particle size distribution. However, as the particlesize of the powders decreases, the composite blend viscosity increases.Thus, the necessary plastic behavior is typically achieved either bylowering the solid content of the composite blend or through theaddition of other organic plasticizers and modifiers to the compositeblend.

By way of further example, referring also to FIG. 3, there is aschematic illustrating certain steps in the fabrication of arepresentative embodiment of an MLCC. The starting materials 21 and 22are first blended 24, 26 to form dielectric and electrode compositeblends. Next, the dielectric composite blend and the electrode compositeblend are separately formed 28, 30 into thin dielectric bodies 50 andelectrode bodies 52. Preferably, the bodies 50, 52 are formed as sheetsin a heated, flat platen press (not shown). Other methods of fabricatingthese sheets may be utilized, such as industrial lamination presses,heated rollers, and extrusion techniques. For the fabrication ofhigh-quality MLCCs, the thickness of the sheets may be, for example, inthe range of between about 0.1 to about 0.2 mm with a variation of about±0.01 mm. The dielectric material may be pressed to form sheets 50having a thickness of about 1 mm, and the electrode material may bepressed to form sheets 52 having a thickness of about 0.5 mm.

Once formed, the sheets 50, 52 are cut or sectioned into strips ofdesired size and configuration using a slicing operation, as at 31.Other methods of sectioning, however, may be utilized, such as diestamping, water jet cutting, laser cutting, and machining for highervolume production. The sheets 50, 52 may be cut into, for example, about1 inch by about 2 inch strips (not shown).

The cut or sectioned dielectric sheets 50 and electrode sheets 52 arenext stacked (as at 32 of FIG. 2) in alternating layers to produce theoffset configuration shown in FIG. 3. The sheets 50, 52 are stacked toproduce a feed rod 36 predetermined dimensions and configuration. By wayof example, a square feed rod having dimensions of about 2 inches longby about 1 inch wide may be formed. It should be noted that the order inwhich the steps of stacking and cutting the sheets 50, 52 are performedmay be reversed, such that a plurality of stacked sheets 50, 52(alternating) are cut at the same time to form strips.

The feed rod 36 is subjected to temperatures and/or pressures effectivefor consolidating (as at 37) the dielectric and electrode sheets 50, 52.For example, the feed rod may be consolidated at approximately 150° C.and approximately 500 pounds pressure. The feed rod 36 then is fed to anextruder 60 having an extrusion cylinder 62 fitted with a taperedextrusion block 64. A ram extruder, continuous extrusion assembly orother suitable extrusion apparatuses may be used. The dimensions andgeometry of the extruder may be adjusted in accordance with the desiredfinal product. The feed rod 36 is then extruded (as at 38, FIG. 2) intoa ribbon 66. The ribbon then may be cut to form un-sintered, or “green,”MLCC chips 62 having thin, alternating dielectric and electrode layers.With reference now also to FIG. 4, the ribbon 66 may be cut at desiredlocations 68 to provide the MLCC chips 62. By way of example, a feed rodincluding BaTiO₃ as the dielectric material and Ni as the electrodematerial may be extruded using a 56° tapered extrusion block havingabout a 1 inch by about 0.1 inch final aperture. A ribbon is producedwith BaTiO₃ layer thickness of about 0.1 mm and Ni layer thickness ofabout 0.05 mm.

The extrusion process may be repeated one or more times as desired todecrease the thickness and increase the number of the layers of theMLCC. The extruded ribbon may be cut and restacked into a second feedrod, which then may be reconsolidated and co-extruded to form an MLCCchip having thinner dielectric and electrode layers than obtained with asingle-pass extrusion process. The present invention allows for theco-extrusion of even finer dielectric layers, with powder particle sizebeing the only limitation on the ultimate layer thicknesses.

As the laminar dimensions and physical properties of the layers have aresulting effect on the performance of the products manufactured by thisprocess, the extrusion process is controlled to produce predictablelayers and properties (such as internal residual stresses). The internalsurface of the extruder itself may be coated with a material, such asPTFE, in order to reduce or even eliminate the frictional effects on thelamina during extrusion. Alternatively, a thin, barrier layer (less thanabout 0.5 mm) of material may be positioned along the sides of the feedrod where the edges of the layers are in contact with the vertical wallsof the extrusion cylinder. Such methods are intended to reduce oreliminate distortions in the resulting extrudate which otherwise mayhave a deleterious effect upon the properties of the finished MLCC chip.

The process as described may be used to provide green MLCC chips. Aspart of the finishing of the green product (as at 42), the MLCC chip issubjected to a polymer bake out cycle and a co-firing cycle (sinteringcycle) in order to consolidate and densify its structure. Thermoplasticpolymers are removed from the MLCC chip in a furnace heated slowly in adesired atmosphere. Design of the binder bake out cycle should considerdegradation rates and temperatures of the binder system of themultilayer structure. The binder bake out cycle is preferably a slowprocess in order to minimize stresses and distortion in the MLCC chipduring pyrolysis of the organics. If bake out occurs too rapidly,bloating, cracking, and delamination will lead to a defective chip. Inaddition, fine metal powders are typically excellent reaction catalystsand can catalyze the polymer decomposition reactions, also leading topart distortion. It is necessary to control the binder bake out profileand to use binders that burn out cleanly, leaving minimal residue (i.e.,carbon), which can reduce the electrical properties of the devices andstructures. Incomplete removal of the binder may leave the componentdisrupted by separation of the dielectric and electrode layers andresult in areas that may cause dielectric breakdown. A binder burnoutfurnace, such as commercially available from Lindberg, Watertown, Wis.may be used to remove polymer binder for the polymer bake out cycle.

After removal of the binder, the MLCC chip is heated to a temperatureand for a period effective for densifying the dielectric and electrodematerials. Sintering occurs in a desired, preferably reducing,atmosphere, such as a nitrogen atmosphere, with only limited or nopressure being applied during the cycle. The sintering behaviors of thedielectric material and electrode material are critical to theproperties of the MLCC. Large differences in the composition of theinitial composite blend, as well as differing sintering characteristicsbetween the dielectric and electrode materials, non-uniform shrinkagedue to volume differences (polymer loading) and coefficient of thermalexpansion mismatch can lead to significant stresses during sintering.Similar to polymer bake out, operating conditions and materialcharacteristics may lead to delamination and cracking of the componentduring the co-firing cycle. Dielectric and electrode materials should beselected to avoid thermal expansion mismatch between the electrode anddielectric layers in order to limit delamination and microcrackingduring cooling from the sintering temperature. After finalconsolidation, a sintered MLCC component 44 is provided. It is expectedthat average layer thickness may decrease during sintering by up toabout 50 vol % or more.

After polymer bake out and final consolidation, end terminations must beformed (as at 46) for the MLCC components 44. Generally, endterminations may be formed by any method know to those of skill in theart, such as by terminating the ends using Ag conductive ink. The choiceof termination metal should consider cost, solderability, and leachresistance. Although many suitable metals may be used, Ag is thecheapest, most commonly used termination material.

EXAMPLES

The following examples further illustrate embodiments of the presentinvention but are not be construed as in any way limiting the scope ofthe present invention as set forth in the appended claims.

Example 1

Typical dielectric composite blends and electrode composite blends areset forth below in Tables 1 and 2, respectively. TABLE 1 MaterialDensity (g/cc) Volume % BaTiO₃ ¹ 5.85 45-75 EEA² 0.93 15-50 HMO³ 0.881 0-10¹BaTiO₃ powder available from TAM Ceramics, Inc. as Ticon HPB gradeBaTiO₃²Ethylene ethyl acrylate³Heavy mineral oil

The batch size is 231 cc. TABLE 2 Material Density (g/cc) Volume % Ni⁴8.9 45-75 EEA⁵ 0.93 25-50 B-67⁶ 1.06  0-10 HMO⁷ 0.881  0-20⁴Nickel powder (<1 μm average particle size) available from Cerac, Inc.⁵Ethylene ethyl acrylate⁶B-67 acryloid resin⁷Heavy mineral oilThe batch size is 231 cc.

Barium titanate powders were purchased from TAM Ceramics, Inc. (gradesTicon TME and Ticon HPB of BaTiO3). The HPB grade has a slightly smallerparticle size (D90=2.5 μm) and were used for the BaTiO3 batches in themulti-layer coextrusions. Nickel powder in the amount of 2.5 kg (lessthan 1 μm average) was purchased from Cerac, Inc.

Example 2

This example illustrates a method of consolidating the “green” product(MLCC chips). The thermoplastic and plasticizer binder system(additives) is effectively removed through a bake-out period. Thebake-out occurs over four days in a nitrogen atmosphere where a maximumtemperature of about 600° C. is reached over the four-day cycle. Thefinal temperature of 600° C. is reached during a ramp-up period duringwhich the temperature is raised by about 0.1 to about 0.2° C./minute.

Example 3

This example illustrates a method of sintering the “green” product (MLCCchips) to densify the ceramic capacitor. When BaTiO3 as the dielectricmaterial and Ni as the electrode material, the MLCC chips initially maybe co-fired in a nitrogen atmosphere at approximately 1150° C. Thistemperature is incrementally increased in order to obtain denserdielectric layers. The final co-firing schedule consists of a ramp ofapproximately 2° C./minute to approximately 1275° C. with anapproximately 150 minute hold at this temperature.

While the invention has been described with respect to specificsincluding presently preferred modes of carrying out the invention, thoseskilled in the art will appreciate that there are numerous variationsand permutations of the above described specific that fall within thespirit and scope of the invention as set forth in the appended claims.

1. A method of manufacturing components having multi-layer architecturescomprising the steps of: (a) combining a dielectric ceramic materialwith a first additive composition to form a first composite blend; (b)combining an electrically conductive material with a second additivecomposition to form a second composite blend; (c) forming a dielectricbody from the first composite blend; (d) forming an electrode body fromthe second composite blend; (e) arranging a plurality of dielectricbodies and electrode bodies to form a feed rod having a patterned arrayof alternating dielectric and electrode layers; and (f) extruding thefeed rod to form a component product having multi-layered architecture.2. The method of claim 1 further comprising a step of sectioning theextruded feed rod to provide a plurality of individual componentproducts of predetermined dimensions and having multi-layeredarchitecture.
 3. The method of claim 1 wherein the patterned array ofdielectric and electrode layers of the feed rod is maintained duringextrusion to provide a component product having essentially the samepatterned array of layers.
 4. The method of claim 1 wherein thedielectric ceramic material is a ferroelectric compound.
 5. The methodof claim 1 wherein the dielectric material is selected from the groupconsisting of titanate compounds, niobate compounds tantalate compoundsand combinations thereof.
 6. The method of claim 1 wherein thedielectric ceramic material is selected from the group consisting ofMgTiO₃, BaTiO₃, BaTi₄O₉, TiO₂, SrTiO₃, CaTiO₃, Al₂O₃, MgO andcombinations thereof.
 7. The method of claim 1 wherein at least one ofthe first and second additive compositions includes a thermoplasticbinder.
 8. The method of claim 1 wherein at least one of the first andsecond additive compositions includes a plasticizer.
 9. The method ofclaim 1 further comprising steps of: (a) stacking the extruded componentproduct to form a second feed rod; and (b) extruding the second feed rodto form a second component product having multi-layered architecture.10. The method of claim 1 further comprising a step of heating thecomponent product to burn out the first and second additivecompositions.
 11. The method of claim 10 wherein heating occurs in anitrogen atmosphere.
 12. The method of claim 1 further comprising a stepof densifying the component product wherein densifying includes heatingto a temperature and for a time effective for densifying the dielectricand electrode materials of the component product.
 13. The method ofclaim 12 wherein densifying occurs in a nitrogen atmosphere.
 14. Themethod of claim 1 wherein the step of extruding includes consolidatingthrough the application of heat and pressure.
 15. The method of claim 1wherein the electrically conductive material is a metallic material. 16.The method of claim 15 wherein the electrically conductive material isselected from the group consisting of base metals, precious metals andcombinations thereof.
 17. The method of claim 1 wherein the componentproduct includes repeated structural units having an orderedmicrostructure, the structural units being disposed across a workingsurface of the component.
 18. The method of claim 1 wherein thecomponent product is a multi-layer ceramic capacitor.
 19. The method ofclaim 1 wherein the composite product is a microwave dielectric filter.20. The method of claim 1 wherein the composite product is an ultrasonicmotor.
 21. The method of claim 1 wherein the composite product is apiezoelectric component.